1. Field of the Invention
The invention relates to a liquid crystal display device and a method of fabricating the same, and more particularly to an in-plane switching mode active matrix type liquid crystal display device and a method of fabricating the same.
2. Description of the Related Art
A liquid crystal display device may be grouped into two types in one of which molecular axes of aligned liquid crystal molecules are rotated in a plane perpendicular to a substrate to display imaged, and in the other of which molecular axes of aligned liquid crystal molecules are rotated in a plane parallel with a substrate to display images.
A typical one in the former type is a twisted nematic (TN) mode liquid crystal display device, and the latter type is called an in-plane switching (IPS) mode liquid crystal display device.
Since a viewer looks an IPS mode liquid crystal display device only in a direction in which minor axes of liquid crystal molecules extend, even if he/she moves his/her eye point, how liquid crystal molecules stand is not dependent on a viewing angle, and accordingly, an IPS liquid crystal display device can present a broader viewing angle to a newer than a TN mode liquid crystal display device.
Hence, an IPS mode liquid crystal display device has been more popular these days than a TN mode liquid crystal display device.
For instance, Japanese Patent Application Publication No. 2000-89240 (Japanese Patent No. 3125872), Japanese Patent Application Publication No. 2000-81637 and Japanese Patent No. 2973934 have suggested an in-plane switching mode liquid crystal display device.
As a typical example of a conventional in-plane switching mode liquid crystal display device, the liquid crystal display device suggested in Japanese Patent Application Publication No. 2000-89240 is illustrated in FIGS. 1 and 2. FIG. 1 is a plan view of the liquid crystal display device, and FIG. 2 is a cross-sectional view taken along the line II—II in FIG. 1.
As illustrated in FIGS. 1 and 2, common electrodes 103 and common electrode lines 105 exist above and overlap scanning lines 101 and data lines 102.
In the conventional liquid crystal display device illustrated in FIGS. 1 and 2, though the common electrodes 103 and the common electrode lines 105 shield the scanning lines 101 and the data lines 012, the common electrodes 103 are formed only on an interlayer insulating film 104, as illustrated in FIG. 2. As a result, the conventional liquid crystal display device illustrated in FIGS. 1 and 2 is accompanied with the following problem.
If the common electrode line 105 is comprised of an electrically conductive transparent film, the common electrode line 105 would have a high wiring resistance, resulting in that a delay occurs in the common electrode line 105, and a crosstalk is also generated in a direction in which the scanning lines 101 extend, in dependence on an image pattern.
On the other hand, if the common electrode line 105 is comprised of an opaque metal film, liquid crystal would make contact with the opaque metal film through an alignment film, and hence, on application of a direct current voltage to the common electrode line 105, the opaque metal makes electrochemical reaction with liquid crystal, and resultingly, is fused into a liquid crystal layer. This causes a spot to be likely to be generated in a display screen.